Pickup device



United States Patent inventor Edward C. Forcier [56] References Cited Worcester, Massachusetts IT STATES PATENTS g m- 33 2 3,438,668 4/19 9 Olsson et al. 294/64 Patented Nov. 1970 3,431,009 3/1969 Mammel 294/64 Assignee Sprague Electric'Company, Primary Examiner-Even C. Blunk North Adam Ma achu tt Assistant Examiner-Roger Si Gaither a corporation of Massachusetts Attorneys-Connolly and Hutz; Vincent H. Sweeney,

James P. OSullivan and David R. Thornton gg fifi Fi ABSTRACT: A fluid flow is provided in radially opposite 8 I g directions over the surface of a work piece to provide lift and a U.S. Cl 294/64 fluid flow is directed over the surface towards depending Int. Cl. B66c 1/02 members of the device to urge the work piece against the Field of Search 294/64 members and restrict its lateral movement.

Patented Nov. 10, 1970 3,539,216

PECKUP Davies BACKGROUND or THE INVENTlON This invention relates to pickup devices and more particularly to a pickup device which restricts vertical and lateral movement of a work piece without contact with the upper surface thereof.

In the prior art, pickup devices which utilize high velocity fluid flow to lift materials are well known. These generally operate by directing a flow of fluid such as a gas or the like in radially opposite directions over the upper surface of the work material so as to lift or attract a work piece towards the device. At the same time, the fluid provides an air or gas cushion so that the material surface does not come into contact with the unit.

While this type of device is suitable for automatic lifting of large sheet material which is to be maintained in a horizontal position, it is not well suited to the lifting and transporting by hand of small units as employed'in the electronic arts; for example, semiconductor wafers or the like. This follows from the fact that the force exerted on the work material by the prior art devices is essentially normal to its surface and lateral movement of the work piece with respect to the apparatus is relatively unrestricted. Hence, the work tends to slide on the gas bearing and fall from the pickup device when it is tipped or moved quickly.

One object of the invention is to provide a device suitable for securely picking up material without deleterious contact with the upper surface thereof.

Another object of the invention is to provide a pickup device which firmly positions work material beneath the device.

A further object of the invention is to provide a pickup device which restricts lateral movement of the work material with respect to the device.

A still further object is to provide a pickup'device having an unbalanced flow of fluid across a surface of the work to bias "40 the work edge against depending members of the device.

SUMMARY or THE INVENTION A pickup device constructed in accordance with the invention comprises means for lifting a body,' means limiting the lateral movement of said body in at least one direction, and means directing a flow of fluid across a surface of said body in said one direction so as to urge said body against said limiting means. v

In a more limited sense, apickup device constructed in accordance with the invention comprises a head adapted to provide a flow of fluid in radially opposite directions across a surface of a body for lifting thereof and an unbalanced flow of fluid across a surface of said body in the direction of depending members of said head for biasing said body thereagainst.

In a still more limited sense, the pickup device includes a hollow head adapted for coupling to a source of fluid under pressure, said head having a pair of 'ports and a depending member on the underside thereof, one of said ports being adapted to direct a flow of fluid inlradially opposite directions over a surface of said body for lifting thereof, and the other of said ports being disposed between said one port and said member, and said other port being adapted to direct an unbalanced flow offluid over said surface in the direction of said depending member for urging said body thereagainst and thereby positions said body beneath said head and restricts lateral movement of said body thereto.

BRIEF DESCRIPTION OF THE DRAWING.

BRIEF DESCRlPTlON OF HE PREFERRED EMBODXMENT FlGS. R and 2 illustrate the pickup device of the preferred embodiment wherein a hollow head 10 is adapted for coupling to a source of fluid under pressure by means of transmission line 12. Head 10 includes a triangular shaped plate 14 which is joined to line 12 to form a fluid chamber 16.

A pair of passageways or ports 22 and 24 extend from chamber 16 through plate 14 and terminate in spaced apart orifices 26 and 28 of the underside or lower surface 32 of plate 14. Ports 22, 24 are arranged to direct fluid across a surface of a work piece 34 such as a wafer or the like which is to be picked up.

Plate 14 also includes a pair of spaced apart fixed members 36 and 38 which extend out of or beyond the outlet end of ports 22 and 24. Members 36, 38 extend out of the plane of outlet orifices 26, 28 and at an angle to this plane. Preferably, the plane of the members is perpendicular to that of the orifices. Members 36, 38 depend from the periphery of plate 14 and provide a positioning means for an edge of the work material 34 which limits lateral movement of the body in the direction of these members. Hence, the members provide a stop for the edge of the body.

In this embodiment, port 22 provides a passageway which is substantially perpendicular to the lower plate surface 32 such that fluid, for example, air or nitrogen or other gas delivered to chamber 16 will be directed in radially opposite directions across the upper surface 42 of the work piece when head 14 is positioned close to and over the latter. This radial flow provides a decrease in atmospheric pressure on upper surface 42 and a substantially perpendicular force on the work piece which biases or attracts it towards head 10. Contact with the underside of plate 14 is prevented, however, by the gas flow which also creates a gas cushion or air bearing between head 10 and wafer 34.

Port 24, on the other hand, is inclined at an acute angle to the underside (surface 32) of plate 14 and provides an unbalanced flow of fluid in the direction of the depending members 36 and 38. This unbalanced flow provides a lateral force (primarily frictional) on the wafer 34 which biases or urges it against members 36 and 38 and hence, restricts lateral movement of the body with respect to head 10. Small angles of inclination (0 to 30) are preferable, however, small angles require a large separation between the outlet orifices since the ports, in this embodiment, lie in the same plane. Hence, an angle of inclination of 15 is preferred in this case.

The gas stream emitted from port 24 also provides slight lift (that is a force substantially perpendicular to the wafer) as well as a lateral force so that there is a resultant force from the unbalanced flow which tends to bias the wafer in a lateral and slightly upward direction against the edge stops. Since the unbalanced flow is emitted between the center of the work piece and stops 36 and 38, its resultant force provides a rotational torque directed upward against the stops which securely holds the wafer against the latter and allows use of the novel device at any angle. Consequently, wafers can be safely lifted from the vertical position in which they are conventionally stored.

It should be noted that although many different arrangements or combinations of the balanced and unbalanced flow are possible, if theunbalanced flow is emitted from a point near the edge opposite the stops or if the position of the ports is reversed, that is, if lifting port 22 is placed between the inclined port 24 and the edge stops there will be a tendency for the wafer to rotate downward along the stops.

Since both the perpendicular and lateral forces on the wafer are functions of not only fluidvolume but also the surface distance traversed by the flow, both ports should be positioned back from the edge of the-work material. Preferably, main port 22 is centered over the material or slightly off center in a direction away from the depending members, and inclined port 24 is positioned close to the main port and between it and orifices will depend upon the angle of inclination of port 24 as well as port diameter, etc. In this embodiment, orifices 26 and 28 are approximately .300 inch from center to center.

In the preferred embodiment, ports 22, 24 lie on a plane which is perpendicular to the plane passing through depending members 36 and 38 and bisects the separation between them. This insures that the lateral force on the wafer will be directed substantially perpendicular to the plane of the stops and on a line bisecting them so as to stabilize the wafer against them.

Two spaced apart stops are employed in this embodiment to allow handling of objects of different shapes. In this case, members 36 and 38 are substantially perpendicular to the outlet plane of the ports and are curved in this plane to conform to the generally circular perimeter of a conventional semiconductor wafer. However, this spaced apart arrangement will ac commodate work pieces of many different shapes such as circular, rectangular, triangular or irregular shaped pieces.

it should be understood of course that since the device utilizes a lateral surface force to position the work piece against the edge stops, the work piece should preferably be substantially rigid. Moreover, in order to develop sufficient lift in comparison to the weight of the work material, a thin substantially planar work piece is most suitable.

Preferably, depending members 36 and 38 are made narrow so as to minimizecontact of the wafer edge. In addition, their inner faces 42 and 44 are coated with a nonmarring and noncontaminating coating such as, for example, polytetrafluoroethylene or the like. Hence, since only the fluid and coated members 36, 38 come in contact with the work piece, head can be made of many different materials such as aluminum or nickel or the like.

The unit may also assume many different shapes. Plate 14 preferably provides a generally planar undersurface for suitable lifting and air cushioning, etc.-, however, the plate may be circular, rectangular or irregular in shape, rather than triangular as shown. Similarly, many different shapes and any number ofdependent members are useful. Preferably, these edge steps will depend from the underside of the head as shown, and will be grouped together to limit lateral movement in one direction. Thus, a number of spaced-apart stops might be employed with the indicated bisecting fluid flow or, alternatively, a plurality of unbalanced fluid flows directed perpendicular to the plane of a single narrow stop may also be suitable. For example, two inclined ports equally spaced on each side of the plane of the lifting port and the single member can be suitably employed. In addition, a single wide stop may also be useful.

The fluid flow, which is a function of port size and source pressure, is determined in accordance with the size and mass of the object to be picked up. The relative flow from each port must also be controlled. In this embodiment, since both ports are in communication with the same fluid chamber their relative flow is a function of their respective diameters.

The inclined port is preferably made smaller in diameter than that of main port since the fluid flow from the former is more concentrated on the wafer. For example, the diameter of the smaller port may be made slightly less than one-halfthat of the main port.

In a specific example, a main port of 0.062 inch diameter and an inclined port of .025 inch was utilized with a source pressure of 15 to lOO pounds to lift conventional semiconductor wafers. The smaller port was inclined at an angle of l5 to the horizontal. In this case, less than 15 pounds did not produce sufficient lift whereas over pounds resulted in vibration forces which tend to crack the fragile wafer.

I claim:

1. A pickup device comprising at least a pair of ports, one of said ports being disposed substantially perpendicular to the upper surface of a body for directing a flow of fluid in radially opposite directions over said surface so as to provide a lifting thereof, at least onemember which extends beyond the outlet end of said ports for limiting lateral movement of said body in at least one direction, and the other of said ports being disposed at an acute angle to said surface for directing an unbalanced flow of fluid over said surface in said one direction for urging said body against said limiting member,

2. The device of claim 1 including a hollow head adapted for coupling to a source of fluid under pressure, said pair of ports being disposed on the underside of said head, and said member depending from said head and extending beyond the underside thereof.

3. The device ofclaim 2 wherein said depending member includes a nonmarring and noncontaminating surface for limiting the lateral movement of said body.

4. The device ofclaim 3 wherein said nonmarring and noncontaminating surface is polytetrafluorocthylene.

5. The device of claim 2 wherein the direction of unbalanced fluid How is substantially along a plane passing through both ports.

6. The device of claim 5 including a plurality of said depending members in spaced relation, and said plane bisects said plurality.

7. The device of claim 6 wherein said head has a substantially planar underside, said plurality of members depend from the periphery of said underside, and said other port which emits an unbalanced flow of fluid over said surface is disposed between said one port and said members to provide positive engagement of an edge of said body with said members.

8. The device ofclaim 3 wherein said other port is smaller in diameter than said one port.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,539,216 Dated November 10, IQZQ Edward C. Forcier Patent No.

Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 49, "claim 3" should read claim 2 ZSlGNED AN Eifi-LED Febuar'y 2, 1971 (SEAL) Attest:

Edward M. Betcha, Jr mm JR.

Comissioner of Patents. 

